Aristotle described the earth as a cold and dry body and paid no attention to the phenomenon of terrestrial heat. Renaissance physicians, by contrast, when seeking to understand the origin of hot springs in the context of their balneological studies, came to defend a theory of subterranean fires. This tradition, which started in Italy, became widely known through the works of Georgius Agricola. But although it had implications for the explanation of further natural phenomena, it remained almost exclusively confined to medical circles. As far as physics as an academic discipline was concerned, the ideas concerning subterranean fire were hardly taken note of. Only with the collapse of Aristotelian philosophy in the seventeenth century could these by then "old innovations" obtain a wider significance.